Conductor ampacity

[david luchini]

I don't see why not. 110.14(C) is just telling us Table 310.16 is the default. Equipment with terminations outside of enclosures for which it makes sense to allow termination ampacities from other Tables simply needs to so "listed and marked" to allow that to happen.

There is no requirement in 110.14(C) for terminations outside of enclosure to be "listed and marked" at all. They can be the same terminations that are used within enclosures.

 

[wwhitney]

There is no requirement in 110.14(C) for terminations outside of enclosure to be "listed and marked" at all.

Agreed, and what you quoted from me does not say otherwise. What it says is that if such equipment wants to use termination ampacities other than from Table 310.16, then it would need to be so listed and marked, per 110.14(C).

Cheers, Wane

 

[solarken]

Terminations means at equipment, like a PV inverter or a breaker or utilization equipment, yes? Then typically those terminations will be in an enclosure, so referencing Table 310.16 as the default seems perfectly reasonable to me. If you have some atypical equipment where the terminations are actually in free air, the language allows the equipment to listed for other termination ampacities.

So I'm not seeing the problem. For your outdoor free air PV application, you can use say an inverter with a conduit riser and weatherhead, and splice at the weatherhead. The conductors between the splice and the inverter would likely be governed by the termination ampacity within the inverter. While the other conductors may be in free air and governed by Table 310.17.

Cheers, Wayne

You can have an enclosure with free air running through it. Free air in the definitions is "Open or ventilated environment that allows for heat dissipation and air flow around a conductor. It is not the same as 3 current carrying conductors in a conduit. It sure seems like there should be some room for reason here. Single conductors inside a large container (relative to the cross section of the conductor) can certainly have a lot of air flow around them, and heat could dissipate into that air.

Many inverters or other equipment have active cooling, with fans and air circulation. It seems odd that 110.14(c) does not just keep to specifying the temperature limits, since that is the subject of that section, and leave the ampacity up to where it belongs, namely 310.

 

[solarken]

What it says is that if such equipment wants to use termination ampacities other than from Table 310.16, then it would need to be so listed and marked, per 110.14(C).

Cheers, Wane

What would the listing and marking look like? "These terminals can use either Table 310.16 or Table 310.17 to calculate ampacities"?

 

[wwhitney]

You can have an enclosure with free air running through it. Free air in the definitions is "Open or ventilated environment that allows for heat dissipation and air flow around a conductor

Thanks for pointing out that definition, it's new in the 2020 NEC and I never noticed it. I wonder what ventilation rate would be required through a 4" conduit to allow the use of Table 310.17. : - )

Anyway, equipment using a ventilated enclosure can choose to pursue a listing allowing a marking for termination ampacity based on something other than Table 310.16.

Many inverters or other equipment have active cooling, with fans and air circulation. It seems odd that 110.14(c) does not just keep to specifying the temperature limits, since that is the subject of that section, and leave the ampacity up to where it belongs, namely 310.

It's only specifying Table 310.16 as a default with respect to the termination ampacity, seems reasonable to me. It doesn't preclude the use of other tables for other portions of the circuit.

Cheers, Wayne